2011 - Cooperative Institute for Research in Environmental Sciences ...

SCIENTIFIC CENTERS
n Center for Limnology
n Center for Science and Technology Policy Research
n Climate Diagnostics Center
n Earth Science and Observation Center
n National Snow and Ice Data Center
Center for Limnology
The Center for Limnology supports research and graduate
education related to biogeochemistry and metabolic
functions of aquatic ecosystems. During 2010, the Center
continued its work on the biogeochemical effects of pine
bark beetles on montane watersheds in Colorado. Strong
disturbance of vegetation by practices such as clearcutting
or herbicide treatment is known to cause radical changes
in the nitrogen cycle of watersheds, as reflected in the
chemistry of streams within watersheds. For example,
classical studies of clearcutting and herbicide treatment
in experimental watersheds of New Hampshire showed a
50-fold increase in the export of nitrate from watersheds as
a result of treatment. Because of the work in New Hampshire
and elsewhere, biogeochemically oriented scientists
in the Rocky Mountain region have anticipated massive
loss of nutrients, and especially inorganic nitrogen, from
watersheds that are severely infested with pine beetles.
Because vegetation takes up nutrients, elimination of vegetation
by any mechanism, including severe pine beetle
infestation, is likely to cause release of nutrients. Nutrient
release has been studied by Center staff, including CIRES
Ph.D. student Leigh Cooper.
The results of biogeochemical studies across a range of
infestation intensities for pine beetle in the Colorado Rockies
have shown effects that range from negligible to very
mild. Thus, the observations are unexpected and require
some explanation. Staff scientist James McCutchan has
proposed an explanation that is derived from the mechanism
of pine beetle infestation. The infestation comes on
incrementally over a period of years. The effect of the
incremental nature of infestation can be modeled by the
use of watershed biogeochemistry models that predict the
loss of nitrate and other nutrients from disturbed watersheds
(Figure 1). Modifying the model to acknowledge
the staged nature of vegetation losses associated with
pine beetle mortality shows that the model predicts what
we are now observing (i.e., a suppression of peak losses
associated with sudden disturbances such as clearcutting
or herbicide treatment). These findings are being prepared
for publication in collaboration with other research groups
working on the biogeochemical effects of pine beetle
infestation.
60 CIRES Annual Report 2011
Top, Bluebird Lake, Rocky Mountain National Park (RMNP). Bottom,
endangered greenback cutthroat, the original resident trout of RMNP.